In the field of photoengraving, in order to adequately deal with the diversity and complexity of printed matter, photographic materials with good reproducibility of the original, stable processing solutions and/or simplified replenishing are desirable.
In particular, in the process of photographing line originals, the original is prepared by sticking photocomposed characters, handwritten characters, illustrations, halftone photographs and the like. Accordingly, in the original, images of differing line width and density are often mixed. Finishing process cameras, photographic materials and image formation methods giving good reproduction of these originals are greatly desired. On the other hand, in the photographing of catalogs and large posters, enlargement of dot photographs (extension) or reduction (contraction) are widely performed by photoengraving using enlarging of dots, but the number of lines becomes coarse, and thus results in the photographing of unfocused points. In reduction, the line number per inch becomes greater and gives rise to a photograph of fine points. Accordingly, in order to maintain reproducibility of dot gradation, an image formation method possessing wider latitude is necessary.
Halogen lamps or xenon lamps are used as the light source for process cameras. For sensitivity to these light sources, usually orthosensitization of photographic materials is performed. However, orthosensitized photographic materials are too strongly influenced by the chromatic aberration of lenses, and it was ascertained that image quality easily deteriorates because of this. Further, this deterioration is more conspicuous for xenon light sources.
As a system responding to the requirement for wide latitude, lith type silver halide photographic materials consisting of silver chlorobromide (at least 50% silver chloride content), processed in hydroquinone developer solution with greatly reduced effective concentration of sulfite ion (usually 0.1 mol/liter or less), is a known method of obtaining line originals and dot images having high contrast and high density of blackening, with the image part and nonimage part clearly separated. However, in this method, because the sulfite concentration in the developer solution is low, development is very unstable to air oxidation, and to maintain stability of solution activity various endeavors and contrivances have been made and utilized; the state of the art was such that processing speed was conspicuously slow, and operating efficiency was reduced.
Because of this, a developing method as mentioned above (lith development system) to remedy the instability of image formation, to develop using processing solutions possessing well-maintained stability, an image formation system possessing supercontrasty photographic properties is desired. One such system, as exemplified in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781 was proposed, wherein a specific acylhydrazine compound is added to surface latent image type silver halide photographic materials at pH 11.0 to 12.3 containing 0.15 mol/liter or more of sulfite preservative, then the material is processed with a developer possessing well-maintained stability, thus forming supercontrasty negative images with gamma exceeding 10. In this type of image formation system, in contrast to prior supercontrasty image formation in which only silver chlorobromide having a high silver chloride content could be utilized, the advantage is that silver iodobromide and silver chloroiodobromide can also be utilized.
The imaging system mentioned above exhibits sharp dot quality, processing stability and speed, and excellent performance in reproduction of the original, but to satisfactorily deal with the diversity of printed matter in recent years, systems giving further improvement in reproducibility of the original are demanded.
On the other hand, in the operation of gathering and contact processes, an increase in processing performance has been achieved by performing operations in brighter surroundings, and because of this, operations can be carried out substantially in daylight surroundings. Thus, development of photosensitive materials for photoengraving and development of exposure printers has advanced.
Daylight use photosensitive materials as described herein are photosensitive materials which can be used with long term stability, using as a safelight a light having long wavelengths of substantially 400 nm or above and not containing any ultraviolet light component.
Daylight photosensitive materials, used in gathering and contact processes, may contain developed film of characters or formed dot images as the original. These originals and reversal photosensitive materials are contact exposed, and negative image/positive image reversal or positive/negative image reversal is performed. These materials are required: (1) to possess negative image/positive image reversal with a capacity for dot imaging and line imaging, and character imaging, each according to their dot area and line width, and character image width, respectively; and (2) to possess a capacity whereby controllability of dot image tone, and controllability of character image line width are possible. So far, daylight contact photosensitive materials capable of meeting such requirements have been provided.
However, in a high level of image conversion work for forming white-on-black letter images through the superimposition contact work, the conventional method of using a daylight photosensitive material and carrying out the contact work in daylight had a defect of providing white-on-black letter images inferior in quality to those provided by the method of using a conventional dark-room contact photosensitive material and carrying out the contact work in dark room.
The method of forming white-on-black letter images through the superimposition contact work is described in more detail below.
As shown in FIG. 1 hereinafter, a letter or line image-formed film (line original) (b) stuck to a transparent or translucent base (a) and a dot imageformed film (dot original) (d) stuck to a transparent or translucent base (c) (wherein a polyethylene terephthalate film having a thickness of about 100 .mu.m is generally used as the sticking base) are superposed, and employed as an original. The emulsion surface of a contact photosensitive material (e) is brought into direct contact with the dot original (d), and subjected to optical exposure.
After the exposure, the contact photosensitive material is development-processed to produce white areas corresponding to line images inside the black dot images.
A point of importance in the above described method for forming white-on-black letter images is that the ideal of negative image/positive image conversion consists in accomplishing the conversion in accordance with individual dot areas of a dot original and individual line widths of a line original, respectively. However, as apparent from FIG. 1, the exposure for printing the line original on the contact photosensitive material is carried out in a condition that the sticking base (c) and the dot original (d) are sandwiched in therebetween, in contrast to the exposure carried out in a condition that the dot original (d) is in direct contact with the emulsion surface of the contact photosensitive material.
Therefore, an exposure determined as optimum for accomplishing faithful negative image/positive image conversion with respect to the dot original is out of focus for the line original because the sticking base (c) and the dot image (d) are interposed as a spacer. As the result, narrowing of the line width of white-printed image corresponding to the line original is caused. This is responsible for deterioration in quality of the white-on-black letter image.
With the intention of dissolving the above described point at issue, systems using a hydrazine compound are disclosed in JP-A-62-80640 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"), JP-A-62-235938, JP-A-62-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-296031, JP-A-63-314541 and JP-A-64-13545. However, these systems cannot be said to be satisfactory, so it is to be desired that further improvements should be introduced thereinto.
As an attempt for making an improvement in image quality, there has been known a method of releasing a development inhibitor in such a distribution as to correspond to silver image from a redox compound containing a carbonyl group, as disclosed, e.g., in JP-A-61-213847 and JP-A-64-72139.
Furthermore, hydrazine was used in the redox compounds of the above mentioned patent disclosures, with the advantages of sharp dot quality, processing stability (for example, changes in the images were small in relation to changes in the developer composition, e.g., pH, sodium sulfite and the like), and the like, but these were insufficient in certain respects.
Accordingly, it was desirable to develop a photographic material using a stable developer forming contrasty dot images and also a wide tone control of the image.